1. Field of the Invention
The present invention relates broadly to refrigerated showcases, particularly open-fronted display and storage cases with air curtains. More specifically, the present invention relates to a refrigerated showcase having an opening through which a consumer can view and access stored items on display. In such a showcase, cooling air is introduced through a perforated interior panel with the coolant air maintained within the refrigerated compartment by an air curtain passed downwardly within the showcase opening. A dual evaporator with at least one fan sandwiched between two evaporator coils supplies the cooling air. Because of the large amount of condensate water produced by the dual evaporator, a three-way solenoid diverter valve directs the condensate water first to a primary dissipater pan and then to a secondary dissipater pan when the primary dissipater pan is full.
2. Description of the Related Art
An example of this type of showcase is described in U.S. Pat. No. 3,696,630 granted on Oct. 10, 1972, to Bressickello who discloses various self-service showcases constructed with front access openings for the purpose of displaying comestibles such as meat, eggs and vegetables. In such showcases, the cooling system includes a refrigerant coil, also known as an evaporator coil, which is located in such a position so as to cool air circulating through the showcase.
A dual evaporator with a reversible fan sandwiched between two evaporator coils is disclosed in U.S. Pat. No. 5,226,285 granted on Jul. 13, 1993, to Dankowski. However, the dual evaporator is used in a self-cleaning heat exchanger for an air conditioning system which requires more electricity than a single refrigerated showcase.
Another dual evaporator for a heat exchanger is described in British Patent No. 1,322,395 published on Jul. 4, 1973. However, the two sets of heat exchange tubes are arranged to reduce the noise level of the fan and not to increase the capacity of the cooling system.
The evaporator or refrigerant coil is sometimes oriented above a relatively small drip pan, also referred to as a dissipater pan, situated in a location so as to collect water condensation from the coil. When the water level rises to a predetermined level, this condition is sensed and a pump is activated to lift the water to an overhead dissipater pan arranged on top of the showcase. The dissipater pan may include a heating coil to dissipate any accumulated water. Other showcases eliminate condensation from the refrigerant coils by a drainage system that communicates with a floor sink.
An example of a showcase of the type where condensation from the evaporator coil is pumped to a dissipater pan arranged on top of a cabinet of the refrigerated showcase is illustrated in U.S. Pat. No. 4,766,737 granted on Aug. 30, 1988, to Baxter, II. In this prior art device, a high temperature coil of the condenser assembly is associated with the lowermost of an array of dissipater pans in order to effect the transfer of heat to the condensate which has been pumped up to the dissipater array atop the cabinet of the refrigerated showcase.
The open-fronted, refrigerated showcases with air curtains in the prior art have reached a level of efficiency such that additional improvements are not readily achieved.
It is well known in the prior art to use perforated wall dividers and/or rear panels which are angled to form an air plenum in association with the back of the showcase. These air plenums are shaped to have a decreasing volume through which cooled air is passed upwardly with the flow also passing through perforations in the wall dividers into the refrigerated showcase. This feature is illustrated in U.S. Pat. No. 3,696,630 previously mentioned and in U.S. Pat. No. 5,345,778 issued on Sep. 13, 1994, to Roberts.
It is also known to route cooled air to a bottom portion of cooling compartments where foodstuffs are stored. Bottom storage bins, where foodstuffs are placed to replenish the display shelves located above the storage area, are commonplace. However, cooling the storage area is difficult to do. Prior art devices have cooled the storage area by diverting a portion of the cooled air which is flowing upwardly from housings in which evaporator coils and air-moving fans are arranged. An example of such an arrangement is found in U.S. Pat. No. 5,345,778 just mentioned.
In accordance with the present invention, three methods of improving air curtains in open-fronted refrigerated showcases have been incorporated in the refrigerated compartment, in the refrigerant system atop the cabinet, and in the air circulation system.
As shall be fully explained below, one purpose of the present invention is to achieve optimal heat exchange by continuously trapping particles suspended in the air that flows into the components of the refrigerant system which over time becomes fouled and impedes air flow and/or the efficiency of the heat exchange. In particular, an air filter pad is used atop the showcase. This air filter pad and a precondenser coil, situated beneath the air filter pad, are both exposed and susceptible to fouling. Advantageously, these elements of the present refrigeration system are cleaned by condensate water originating at the dual set of evaporator coils. This condensate water is pumped from a lower drip pan up to the top of the showcase where a three-way solenoid diverter valve is located.
The three-way valve first directs the water to a primary dissipater pan where the water is heated and then evaporated by hot freon passing through the precondenser coil sitting on the bottom of the primary dissipater pan. When the primary dissipater pan is full, a liquid-level float valve switch is activated and sends an electrical signal to the three-way valve to stop the flow of water to the primary dissipater pan. The three-way valve then diverts the flow of the water to a secondary dissipater pan where the water is heated and evaporated by a heater coil. When the secondary dissipater pan is full, the water flows out through a trough onto the air filter pad which is cleaned by the water flowing down through it. The water then drips from the bottom of the air filter pad onto the precondenser coil which is cleaned in the primary dissipater pan. While the secondary dissipater pan has been filling up, the primary dissipater pan has been emptying because the precondenser coil has been continuing to evaporate water therefrom. The secondary dissipater pan also has a liquid-level float valve which sends an electrical signal, when the secondary dissipater pan is full, to the three-way valve to stop the flow of water thereto. The three-way valve then diverts the flow of water back to the primary dissipater pan which will be empty or almost so. The precondenser coil, preferably made of copper tubing, is inserted into the primary dissipater pan in the gas flow line between the compressor and the condenser coil. As the refrigeration gas is sucked from the evaporator coil below, the compressor places the gas under a higher pressure, thus raising the gas temperature. The hot freon gas is then pushed into the precondenser coil which has a sufficient length to evaporate the water that lands in the primary dissipater pan. The lengthy copper tubing coil between the compressor and the condenser coil functions to evaporate the water which has collected during the operation of the refrigerated showcase. The precondenser coil is situated in the primary dissipater pan, suitably resting on the bottom of the pan, with at least a portion of the coil exposed to the atmosphere in the open section of the top of the showcase. The precondenser coil also sits forward of the face of the air filter pad. Preferably, a major portion of the precondenser coil is exposed to the atmosphere. The precondenser coil also assists the condenser coil by precondensing the refrigerant. The air is pulled through the space where the air filter pad, precondenser and the primary dissipater pan are located. The air then circulates outside the precondenser coil and acts as a heat exchange medium. Precondensing refrigerant gas into liquid, moreover, makes the condensing system more efficient.
The present invention also provides an apparatus for assuring proper cooling at the bottom of the refrigerated compartment of the showcase.
The multiple fans, which move cooled air over the evaporator coils situated in the bottom of the refrigerated compartment, reduce condensation on the evaporator coils that are used to cool the air circulating in the showcase so that icing is reduced on the evaporator coils.
Water collecting on the evaporator coils is captured in an evaporation tray situated below the evaporator coils and is pumped to the top of the showcase where the condenser is located. At the top, the water flows into either a primary dissipater pan or a secondary dissipater pan which has a trough that passes the water down through the filter pad which functions to remove particulate matter and other foulants from the filter. The water from the evaporator coils both clean the air filter pad and cool the air passing through the air filter pad before the air contacts the condenser coils of the refrigeration system. The water runs down through the air filter pad into the primary dissipater pan and then onto the precondenser coil carrying refrigerant from the compressor. This precondenser coil is thus cooled by cold water originating at the evaporator coils below. The filtered air passing over the condenser coils, which air is further cooled by contact with the water, passes over and/or through the air filter pad before absorbing heat produced during refrigerant condensation. At the same time, the rate of evaporation from the primary dissipater pan, in which the precondenser coil lies, is substantially increased and the risk of water overflow is minimized. The heat generated during compression is exchanged through both the condenser coils and the precondenser coil. The latter comprises another set of coils located downstream of the condenser coils. The precondenser coil in essence functions as a heating coil to assist in the evaporation of water from the primary dissipater pan using the heat of condensation, thereby providing two desirable functions with the energy available within the refrigeration system itself, namely removing heat from the compressed refrigerant and adding heat to the condensate which accumulates in the primary dissipater pan.
Furthermore, the present invention relates to a self-service refrigerated showcase having therein an enclosure for the display of cooled foodstuffs. The enclosure has a front access opening defined by top, side and bottom housing panels. At its sides, the enclosure is defined by vertically elongated strips corresponding to the side housing panels. This enclosure provides access to the foodstuffs on display.
Also, the enclosure has other advantageous features which will become readily recognized from a study of the drawings in conjunction with the following detailed description of the invention.